This invention relates generally to an evacuated medical device and more particularly to an improved vacuum indication for devices utilizing an evacuated vessel for the performance of a curettage or some other type of medical procedure.
The present invention relates generally to and is disclosed in conjunction with an improved device as illustrated in Applicant's prior application, Ser. No. 676,759 filed Apr. 14, 1976, now U.S. Pat. No. 4,063,556. For purposes of completeness, the disclosure of said prior application is incorporated herein by reference.
By way of background, it will be noted that evacuated medical devices for performing curettage and other medical procedures are known. The prior art devices, like the device of said prior application, and as illustrated herein, generally include an evacuated vessel to which is attached a medical implement, such as a cannula, with some form of valve means being employed to apply a vacuum to said implement. These prior art devices, however, to the extent the inventors are aware, and with the exception of the embodiments in the above-cited application, do not utilize means for indicating whether a sufficient vacuum is present within the vessel.
With specific reference to the above-cited application, it will be noted that the indicator means thereof generally comprise an elastomeric member, such as a tube or bellows in which a residual quantity of air at atmospheric pressure is contained. The elastomeric member must expand upon the evacuation of the vessel to give an indication of the vacuum level. However, if the elastomeric member should leak, due to pin holes or the like being formed therein the residual quantity of air will seep into the vessel tending to produce an equilibrium condition, with the elastomeric members retracting to their original shape. This return to the original shape, would most likely be construed as an indication that the vacuum in the vessel had been lost, when in fact it had not. As such, fully usable, evacuated units have been discarded due to this erroneous indication. The present invention, however, contemplates an improved, reliable indicator member not subject to any residual elastomeric forces which might give rise to a false reading.
In addition to not being subject to the above-noted disadvantages, the device of the present invention is also possessed of other advantages and features which will become more readily apparent upon a consideration of the following descriptions in conjunction with the attached drawings and detailed discussion of the illustrated embodiment. More specifically, the vacuum indicator of the present invention employs a closed bottom cylinder in which is disposed a piston member. The piston member, includes sealing means in slidable contact with the cylinder's interior wall. The closed bottom of the cylinder includes a recessed portion such that upon disposition of the piston member in the cylinder a residual quantity of air will remain trapped. In addition the present invention contemplates means for maintaining the co-axial orientation of the piston member, and also means to preclude ejection of the piston from the cylinder when the vessel is evacuated. As will become apparent, the quantity of residual air trapped, determines the sensitivity of the indicator and the length of the stroke of the piston upon evacuation of the vessel. Accordingly, upon evacuation of the vessel, due to the residual air at atmospheric pressure a pressure differential will be created across the piston, causing it to move axial of the cylinder. As the piston moves, the quantity of residual air is expanded and its pressure drops. The pistion, theoretically and given a chamber of sufficient length will continue to move until a state of equilibrium is reached, i.e. wherein the pressure differential is no longer sufficient to overcome the sliding frictional forces produced by engagement of the piston with the cylinder side walls. In the present invention means are provided for terminating movement, at a point determined, taking into account the quantity of residual air, as sufficient for indicating an acceptable vacuum level.
With regard to the above discussion concerning the prior devices, and their problems, it should be noted that with the arrangement discussed above, and to be described in greater detail hereinafter does not rely upon exposure of an elastomeric member to obtain an indication of a vacuum. As such, the problem of false indication of loss of vacuum will not occur. More specifically, assuming an evacuated vessel and movement of the indicator to a given location, should the O-ring seal leak but the cover seal remain effective, the pressure differential across the piston might be lost, but it never will be reversed such as would cause the piston to move upwardly toward the closed end. On the other hand, if the cover seal leaks, the vacuum in the vessel will be lost and as air enters the vessel the ambient pressure will rise. Soon a level will be reached which is greater than the pressure on the closed side of the piston (keeping in mind that this pressure is less than atmospheric due to expansion of the residual quantity of air pursuant to initial movement). Accordingly, a pressure differential will be created causing the piston to move upwardly to a position wherein a visual indication is provided to the effect that the vacuum has become lost. The only possible instance wherein the device can provide a false reading is, if the O-ring seal fails and then subsequently the cover seal fails. Should this rather unlikely sequence of events occur, the indicator would register an acceptable level of vacuum when in fact none exists.
A preferred form of the present invention will be discussed and is illustrated in the drawings, and it should be kept in mind that said discussion and illustration are not intended to define the limits of the invention. To the contrary, it is contemplated that those skilled in the art and possessed of the present disclosure, may devise various alternate structures, constructions or modifications, which fall within the spirit and scope of this invention as defined by the claims appended hereto.